Unfortunately, no. However, here is how to get around this limitation. We build a lot of tournament trail cards for some Bassmasters, FLW, SKA, and other tournament guys and this is what they do:
1. Load a card for an area they are fishing.
2. Fish the tournament.
3. Make a backup to a SD card with all new spots they marked and tracks/trails around the inlet/lake and to the fishing grounds.
4. Remove SD card and store for next time and/or pull into Garmin Homeport for management.
5. Delete everything from the GPS unit.
6. Repeat.
So, just make sure each list/file of waypoints is less than 5,000 spots and create multiple cards for the areas you plan on fishing.